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Is it difficult for a GA aircraft to escape a thunderstorm?
I live in the midwest, and I'm getting ready to start working on my PPL.  For some reason I find myself really nervous about getting into the air and suddenly seeing a line of thunderstorms rolling in from the southwest.  In my mind it feels like a fast moving front would be difficult to escape...
But I wonder if my fear is wholly unjustified.  So I thought I'd ask:
If I'm in a GA plane (like a Cessna 172) and I see a thunderstorms forming to my southwest (lets say 20 miles away),  how much time, in general, am I going to have to get on the ground before the storm gets to me?  If I turn away from the storm, and start looking for an airport, will I be able to put distance between me and the storm to buy time to get on the ground?

Just to clarify before I get a lot of "that's what preflight briefings are for", this questions assumes there was a preflight briefing.
But thunderstorms have this tendency to show up unannounced where I live (or at least it feels that way to me), and that's what this question is about. What do I do when a thunderstorm, that I wasn't aware was going to be there, suddenly shows up on the horizon headed right for me?

Your first line of defence would be to never find yourself in such a situation. That's what pre-flight briefings are for.

@J.Hougaard Trust me, I'd never take off on a summers day in Missouri without first checking the weather.  What I'm paranoid about is what to do when thunderstorms decide to show up, despite the fact they were not forecast.

Some isolated CB's might appear "out of nowhere" during days with high convective activity and an instable atmosphere. Just fly around them. It's also pretty easy to estimate the likelihood of this by conducting a proper weather briefing (a diagram of the temperature gradient is a good place to start). Fast moving fronts and squall lines do not just appear "out of nowhere". Have a look at sigwx and frontal charts before you go flying.

The Cessna 172R is given as having a cruise speed of 122 knots, and a $v_{NE}$ of 163 knots. (Check the specifications for the model you have in mind.) 163 knots is 302 km/h is 83.9 m/s is 275 ft/s. What wind speeds do you anticipate at the cloud layer altitude? Unless you expect winds aloft to be at least twice hurricane speed and for these to be maximally unfavorable for you, then mathematically, you should be able to outrun even an unforeseen thunderstorm system that you see forming.

@MichaelKjörling In addition, if the wind is moving a CB toward you at 50 knots, then it is also moving your plane in the same direction (away from the CB) at 50 knots. Planes are subject to wind just like clouds are

@J.Hougaard Well, I took out the reference to squall lines in the question, because you're right about those being hard to miss in a briefing.  I'm still not finding your comments particularly helpful though, I'm not asking about if I should do a briefing, I know I need to do a briefing, I alluded to it in the question (then added it in during an edit to make sure I was clear.)  I want to know what will happen/ what to do if that safety net fails somehow.

@J.Hougaard Indeed, but I ran out of comment space and felt I had made the point clearly enough. :-) (Come to think of it, I might actually turn it into an answer...)

This question seems to be purely about "what happens if I end up in a thunderstorm cloud" not "how can I avoid accidentally flying into a CB or thunderstorm"  I think  the latter would be a great question to ask separately, but shouldn't be addressed in detail here.

@CodyP The questions is about what to do to avoid flying into a thunderstorm (it's why I mentioned the storm being 20 miles away.)  What happens if you end up in a thunderstorm cloud is this: "Wind sheer tears your tiny little GA craft into small pieces and you die a terrible death."  That's why I'm asking about avoiding thunderstorms in a GA craft. (source: http://www.nydailynews.com/life-style/obama-pilot-thunderstorms-crash-plane-article-1.2248409)

@JayCarr  Ok.  i misunderstood your comment about preflight briefing then.

@J.Hougaard The part about the relative wind isn't always true (sometimes, but not always.) Especially during the conditions where CBs happen, winds can be very different (even entirely different directions) at different altitudes.

If you take off with a storm 20 minutes away from the airport, it won't have been "unforecast"; the NWS is much better than that. They can pretty accurately predict what's going to happen regarding various fronts at least 24 hours in advance, in turn giving you the advance notice to adjust your flight schedule to ensure you can get around the storm or well away from it.
But let's say someone goofed (probably you), and now you find yourself climbing into the air off the tarmac with the leading wall of a cumulonimbus looming over the horizon, which will be between you and your intended destination before you reach it.
First rule; never fly toward the storm. Cumulonimbus formations are deadly to small craft, and even commercial airliners prefer to stay at altitude in a holding pattern well above the storm and let it pass by before attempting to land. These "thunderheads" produce torrential rains, powerful and frequent lightning, strong updrafts, hailstones ranging from pebbles up to grapefruit, and turbulent cyclonic winds that can culminate in tornadoes. Your Cessna 172 stands no chance.
Flying away from the storm will, at worst, gain you the time between the storm's speed and yours that you can use to find an open airstrip and put down. As Michael Kjorling said in his answer, most Cessna 172 variants cruise at over 100kts, which would require the storm moving across the ground as fast as a Category 2 hurricane rotates, so in most scenarios even if you're flying in still air with the storm moving over the cooler air you're flying in, if you just put the squall line to your rudder you should gain ground. Ideally, the storm will be pushing a mass of air in front of it which will give you a tailwind, and thus you'll be able to put that much more distance between you and the storm front.
Second rule; unless your planned flight is a cross-country flight heading pretty directly away from the incoming front, get on the ground as quickly as you can do so safely, and find a shelter for your aircraft. Obviously, being at your home FBO where you rent your tiedown or hangar is best, but anywhere you can slip your aircraft under a roof or awning for a couple hours will do. Remember that unless you have your instrument rating, the conditions during and after most thunderstorms are IMC and thus illegal (and deadly) for you to fly in.
If you're flying a pressurized aircraft, and/or you have instrument privileges, you have more options, the best of which is to get above the storm and wait it out. However, your Cessna 172 is not pressurized, so unless you have an oxygen bottle aboard (and are endorsed to use it) you're limited to about 12,500 feet and only for a half-hour, well below the top layers of a thunderhead, so you'll have to outrun it, get around it, or put down and shelter in place while it blows over you.

The NWS most certainly cannot predict the position of a pop-up CB 24 hours out. They can tell you the probability of a CB passing over a given position within a several-hour period that far out, but they have no idea where the actual individual CBs will form until they start forming. Of course, at 20 miles out, you can simply look up and you'll see it. Those things are huge and can be seen from many, many miles away. Once you're airborne, you can see the towers from over 100 miles away, provided there aren't other clouds blocking your line-of-sight.

"the best of which is to get above the storm and wait it out" Unless you have an aircraft with a ceiling similar to that of an SR-71, this is a really bad idea. CBs can go over 50,000 feet and commonly go over 40,000. Also, conditions after a CB passes aren't necessarily IMC. During obviously is, but the IMC is probably the least of your concerns at that point.

Practically speaking this isn't much of an issue, at least under VFR and if you're paying attention. Thunderstorms take some time to form, and as long as you can see them you can avoid them.
I'm assuming you're asking here about isolated thunderstorms, the kind that form in late afternoon in hot, muggy conditions and aren't part of a frontal system. Typically - at least in places like AL, TN, KY etc. - you get a widespread broken cumulus layer, with isolated thunderstorms building up in spots where conditions are more favourable. Something like this:
By Jessie Eastland (Own work) CC BY-SA 4.0, via Wikimedia Commons
Whether you're above or below the broken layer, a storm like that is usually very visible and you can easily fly around it. Above the layer you can see the towering cumulus; below it you can see the rain and probably also the build-up, through gaps in the clouds. You might also have ADS-B or another weather source in the cockpit but the data is already a few minutes old when you get it. It can still be a good way to get a picture of the overall direction that the storm's moving in and whether it's growing or not, but it's definitely not something you can use for real-time flying around a storm; your eyeballs are best for that.
When you see a build-up or an actual storm, you need to assess how far away it is, how severe it is, and which direction it's moving in. You can usually do that visually, but cockpit data can help. Then, simply plan to fly around it. You mentioned 20 miles, which is the distance the FAA recommends to keep between you and a thunderstorm, to avoid turbulence, hail and other unpleasantness (like your passengers getting sick). If you decide that you can't fly around it safely, considering the overall weather situation, terrain, fuel etc., then just land somewhere and wait it out.
But do make a clear decision on what heading to fly; never keep flying towards a storm or large build-up to 'see how it looks'. If your new heading isn't working out the way you want, then aim further away from the storm or turn away completely. A VFR cross-country flight in the South in summer often ends up being a series of extended zig-zags to work around the build-ups. Personally I think that if you're on top of the broken layer it's beautiful and and watching the towers build up is fascinating, but don't get too close! And the towers do build up over time, a thunderstorm - even a small one - is far too massive to just appear out of nowhere, so you really have to be doing something wrong to get caught close to one, at least in the weather conditions I'm describing here.
Under IFR, things are a little different because you have a specific route to follow but in the end it's surprisingly similar to a VFR flight. In summer you'll hear IFR pilots at all altitudes and in all types of aircraft (including airliners) asking ATC for a deviation:

N12345: Center, N12345 requesting deviation 10 degrees left for a [cumulus] build-up
  Center: N12345, deviation approved as requested, report direct ABC VOR when able

That's exactly what the VFR pilots are doing too, you just need ATC's permission for the heading changes under IFR. And I made some other comments about VFR/IFR and storms in this answer; they might be relevant here.

Your assumption in the second paragraph is the case the question is explicitly not asking about: it refers to a "line of thunderstorms" in the midwest, not isolated thunderstorms in Alabama, Tennessee or Kentucky.

@DavidRicherby If you look at the edit history and the comments, you'll see that originally the question asked about "a line" of unforecast thunderstorms, but the OP removed it because he agreed that it's hard to miss a squall line in a briefing. My understanding is that he is indeed asking about isolated or 'pop-up' thunderstorms, which are very common in the South and many other places.

OK but I'm a bit confused. The edit history says that the question hasn't changed since half an hour before you posted your answer. (I checked for that before I commented, since "the question changed after I answered" is a common reason for this kind of mismatch.)

@DavidRicherby You can see it in revision 3 from yesterday, and this comment

First thing first, although it is already mentioned, weather forecast is covered in the briefings. If the atmosphere favors thunderstorm formation, there are signs to look out for.
Now, thunderstorm clouds don't form out of nothing - meaning like, if you got "CAVOK", unless you do your takeoff 4 hours later, chances of you encountering a thunderstorm is very slim. Pre-thunderstorm clouds are usually observable 1~2 hours before the you see rain and lightning. Many people do not realize this simply because they seldom look up the sky. Signs will include low altitude cloud covers, fast changing cloud shapes etc. You will learn in your ground school how to name and identify clouds.
Thunderstorms that form quickly also dissipate quickly. In tropical areas, e.g. Singapore, it is pretty common to have a sunny morning followed by rainy afternoon. However, the area of the thunderstorm is quite small. They are not like massive systems which stretch across states. You should be able to outrun the storm or wait for it to move away without running out of fuel. Often, there will be holes around 10~20 miles wide between storms.
One thing to watch out for is small-area storms with intensity. One of the AOPA lectures mentioned this as the "weather gradient": unlike massive weather systems, where the change from light chop to moderate to heavy turbulence is a long distance, you get from smooth air to turbulence air in a very short time when you encounter these type of clouds. The bad thing is things go bad very quickly. The good thing is safety is often not far away. Always know your heading, and practice making a 180 turn with instruments alone.
If you need to get down, be sure to know where are your alternate airports all the time. It goes without saying the same applies to other emergencies as well. If you have a rough engine or you start feeling dizzy, you better be turning your plane towards the runway instead of scanning your aerial chart nervously looking for the airport symbol.
Lastly, learn how to obtain weather updates while en-route. Your Cessna 172 likely would not have a weather radar, but there are other ways to keep yourself updated - satellite links, radios, etc. If you tune yourself to the local flight-following frequency, you can hear pilot reports from planes ahead of you (you can just listen and not use flight-following). Or you can try the AWOS station 30 miles away. If you're using a satellite link for a radar image, be aware that the images are usually 5~15 minutes old. Never try to navigate through a storm with satellite images. The storm will have moved by the time you think you're in the clear hole. However you can use it to spot rain clouds 80 or 100 miles away.

Side story: there is a story circulating the local flying club from around the 80s or 90s. At that time, GA planes share the only airport, which has only one runway, with commercial airliners. To keep things speeded up, GA planes which depart in the afternoon are not allowed to come back until 2~3 hours later (unless it's an emergency), since sequencing a C172 between two B747s is a nightmare when the airport is operating near full capacity.
So, one GA pilot departed on an afternoon, and he really didn't like weather on his climb out - clouds were nearly overcast behind a mountain, and 2000 ~ 3000 feet was nearly IMC. He radioed in asking if he can land. The controller asked, "How is the weather out there?" The pilot was so nervous and so worried about the weather, he keyed his radio and transmitted:
"The weather is bad bad bad bad bad bad bad bad bad!"

It's the bad bad bad bad weather in the mad mad mad mad world?

”You will learn in your ground school how to name and identify clouds." Oh good, maybe someday I'll be able to use the cloud types that I memorized in 6th grade!

Going by the figures given by Wikipedia, the Cessna 172R has:

Cruise speed 122 knots
$v_{NE}$ (never exceed) 163 knots

I also checked the corresponding numbers for my club's Cessna 172N in its POH, which gives $v_{NO}$ as 128 KIAS (126 KCAS) and $v_{NE}$ as 160 KIAS (158 KCAS). For the purposes of this answer those are close enough, as well as slightly faster (so using the figures from Wikipedia means we're wrong in the direction of safety). For completeness' sake, this aircraft's POH gives $v_{A}$ as 97 KIAS for 2300 lbs, dropping practically linearly to 80 KIAS for 1600 lbs, with KCAS just a hair below (same or one knot slower).
Obviously, you'd want to look up the numbers for the model airframe you have in mind, but the above should be good for a starting point.
Because you really want to get away from that storm system, let's assume you are doing your best to move away from it. I'll consider three scenarios: at maneuvering speed (calling it 90 KIAS); at cruise speed (122 KIAS); and at just below $v_{NE}$ (calling it 160 KIAS).
90 knots is 167 km/h, or 46.3 m/s.
122 knots is 226 km/h, or 62.7 m/s.
160 knots is 296 km/h, or 82.2 m/s.
An all-out hurricane is considered to begin at wind speeds around 30 m/s.
If the winds at the cloud layer altitude is pushing the clouds toward you, and you are maximally unfortunate (equally strong winds in the opposite direction, directly from the direction you want to go; I don't know how that would be possible at any reasonable altitude), then:

At maneuvering speed, the storm will be approaching you at about 16 m/s
At maximum cruise speed, you will be keeping pace with the storm system, but not really getting away from it
At near $v_{NE}$ in something resembling level flight, you will be moving away from the storm system at about 20 m/s

A more likely scenario is that the wind direction is similar at your altitude as that of the storm clouds, which means the wind will be pushing you and the clouds equally. This causes your speed relative to the clouds to be your indicated air speed reduced by the wind speed, which at cruise speed and hurricane winds means you are moving away from the storm system at a significant speed; even at 90 KIAS, you're still moving away from it at about 16 m/s.
Thus, if you see a storm system forming directly ahead, and you make an about-face turn, mathematically, you should be able to outrun the storm system just fine without over-stressing the airframe; likely without anywhere near over-stressing the airframe. As long as the storm system doesn't form practically on top of you, you can most likely just leisurely cruise away from the storm system and land at the nearest appropriate airfield with no significant worries. As long as you head for calm conditions, even a totally unforeseen storm developing (which, as has been pointed out, is highly unlikely in practice) shouldn't be that difficult.
A suitable fuel reserve and a cool head would appear to be sufficient for getting back down on the ground relatively safely, if perhaps not in the exact location you intended when taking off. Some practice operating the aircraft in turbulent conditions might help.

I appreciate any feedback on any relevant aspect I might have overlooked. I'm not a pilot, I mostly just play one on the computer from time to time.

Unless you are in a dive, hitting anywhere close to Vne in the 172 is going to be difficult. Even at full throttle in level flight you aren't going to hit that speed. Not that it really makes a difference, even at cruise speed you are probably going to outrun it. The issue is that convective currents from thunderstorms often extend out 20+ miles from the cloud bases. This is most dangerous in the landing phase, although turbulence can rip the aircraft apart before you even get close.

@RonBeyer Fair point. How do you feel about it now?

@MichaelKjörling I'd use a speed of 130kt IAS, rather than Vne. 130 kt is roughly Vno (Maximum structural cruising speed). Vne is for smooth air, which you're unlikely to encounter near a thunderstorm even when running away: Vno is the non "smooth air" equivalent, and 130 kt also more of an achievable airspeed in level flight. You'd also be recommended to stick to Va (manoeuvring speed) if things get rough, which is more like 100 kt. Using 100kt and 130kt for your "worst/best case" speeds would suit the C172 better

If you're going to be doing the math, you will want to factor in how much time it takes to actually line up at a runway, slow down for landing, get on the ground, taxi and tie down before the storm hits.  Keeping in mind that fuel may be limited as well.

1) Preflight planning - as mentioned above modern meteorology can quite accurately predict where convective activity will be at least 24 hours in advance of your flight so you will know if there is a high risk of thunderstorms along your flight path.
2) Obtain a standard weather briefing prior to your flight.  The briefer can give you area and terminal forecasts at your departure and destination, applicable AIRMETS, SIGMETS and Convective SIGMETS along your route.
3) Local conditions - remember, thunderstorms require three ingredients to form: unstable air, moisture and an orthographic lifting factor.  If any of those items are not present, a thunderstorm will not form.
4) Don't let yourself be painted into a corner.  This is good advice for any flight planning; always have a backup plan - and backups to the backup plan.  Carry extra fuel.  Andicipate alternate or divert routes should adverse weather form along the way.  The good news in the Midwest is that you can practically open any place on any char and find an airport nearby.  If you are flying with a GNSS navigation system the NRST function will give you the name and heading to any public airport Nearest to your current position.
5) Climate factors - the good news is in the Miswest thunderstorms form along frontal easily anticipated frontal boundaries.  Summertime in Florida is another matter where airmass thunderstorms pop up all over the place and develop very rapidly.  The bad news is that Midwest squall lines are some of the most powerful storms on the planet next to cyclonic storms, so stay well away from them.
6) Making use of NEXTRAD and satellite weather products in route.  These have become excellent resources for pilots.  Be aware however, there is an much as a 15-minute delay in the NEXTRAD picture; NEVER rely on it as an instantaneous picture of the weather environment but use it instead as a trend information source - to indicate where storms are moving or developing in.  Remain at least 20nm clear of yellow or red cells or other areas which indicate a storm may be present.

There's a lot of detail above but rather than repeat, I add there is a big difference between a FRONTAL thunderstorm line and isolated thunderstorms (that are common in the midwest and rare at the code). Isolated thunderstorms are relatively easy to avoid by going around them. Frontal lines are difficult.
I also clarify that airliners do not generally go above thunderstorms. Thunderstorms usually rise to over 50,000 (or higher) and they can grow very quickly.


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Would a roll cage plus a safety harness make a small GA aircraft accident more survivable?
It seems to me that race cars (like Formula 1 and NASCAR) and small GA aircraft (like a Cessna 172 or Piper Cherokee) travel at generally the same speeds, roughly between 70 and 200 mph. Yet, if an accident happens, you appear to be more likely to die in a small plane than a race car.**
I figure this may have to do with some of the safety features of race cars versus the safety features of GA aircraft. The main features being the racing harness and the roll cage.  (And also, as Freeman pointed out in a comment, the HANS device and the helmet help quite a lot as well, especially in frontal impacts.)
I know roll cages weight about 80lbs and that they aren't cheap, and I know a safety harness can be difficult to put on and people might not like using them, and I know a HANS device can be cumbersome, as also a helmet can be. But forget all of that for a moment. I'm not asking about why we don't use them from an economic/utility perspective.
What I really want to know is if putting these in a small airplane would be of any benefit to begin with. It's true that they are massively helpful in racing vehicles, but I wonder if the forces racing vehicles face during a crash are markedly different than what you would find in your typical GA crash (e.g., perhaps aircraft accidents happen at less predictable angles, or involve more torsion, etc.). And if perhaps those differences in forces make the use of a roll cage and a safety harness kind of pointless in a small plane because they can't actually help in that kind of accident.
So, would all of these racing safety devices actually make a GA crash more survivable, or does the nature of GA accidents make their use less effective than they are in a race car?
** Try as I might, I couldn't find hard stats on "deaths per accident" in either area.  So this is mostly an impression I've gained from reading a lot of NTSB reports and watching a lot of racing. The fact may be debatable, but shouldn't detract from the main question.

Airplanes do have 3-point (at the minimum) seat belts. About roll cages, they are not practical as airplanes do not roll like racing cars do in an accident/crash. Same reason can be for not using 4- or 5-point seat harnesses.

@Farhan Race cars do actually get into head on collisions with barriers fairly often, and I've seen several aircraft reports where the plane rolled...  I'm wondering if there's more to it than that though.  Feel free to post an answer saying something similar though.

One thing to note is that in a race car, there are always safety crews nearby, which is not true on a small plane. If getting out of a safety harness and roll cage is not easy, that could be enough to explain it, particularly because I think aircraft accidents are more likely to have post-crash fires than car accidents.

In auto racing, drivers have survived impacts of 10+G and walk away. I believe it's a combination of roll cage, 6-point harness, HANS Device, helmet, neck roll, and the extensive crash testing every chassis must go through before being allowed to race. Putting airframes through that kind of crash-testing would most certainly increase survivability of accidents. Then, you get into economics & certification...

@FreeMan HANS Devices, I'd forgotten those.  Another huge step forward for any head on crash.  I'll add that in in a second.

@raptortech97 In every series I've seen all of the safety devices are designed to be driver removable (you never know how long it will take the safety crew to get there on a large track.)  And this is done precisely because of the fear of a fire starting, so...  I think we've got that point well covered.

@Farhan Not all airplanes have 3-point harnesses. The Cherokee I fly doesn't. Actually, none of the airplanes I've flown have had them. Newer ones probably do, though.

One thing I question is the rate of stopping.  In a crash often the rate of deceleration is the critical factor.  Airplanes have a high rate of deceleration when they hit the ground or fixed objects.  Probably more akin to what a street vehicle see when it hits a stationary object light a light pole or parked car.   It might be instructive to see how street vehicles fair when they have similar impacts speeds.  I suspect airplanes will do pretty well in comparison.

@Farhan Many aircraft don't have 3-point restraints as reirab pointed out. Shoulder harnesses became required for the front seats of small aircraft July 18, 1977 & for all seats on December 12, 1986 -- There are lots of aircraft flying that were built before those regulations took effect :-)

I believe some crop dusters do include a roll cage.  Safety harnesses vary by model.  As some have noted, older aircraft may have nothing more than a single lap belt.  Aerobatic planes typically have a 7 point harness (2 shoulder, 2 independent lap belts, and an anti-submarine strap)

There is some good information on F-1 roll structures here : http://www.formula1-dictionary.net/roll_structure.html

@FreeMan: Actually, the record is 214 Gs (no, really).

@JerryKur  I think you are touching on the point I wanted to make, which is that race circuits are continually being improved to try and ensure that a collision on track doesn't turn into a crash off-track, if you get what I mean? On the other hand, rallying is probably a better comparison, but even there, it is quite common for an accident to occur in several stages, losing a little bit of energy at each point, whereas aircraft tend to impact 'all at once'.

Short answer: Yes, a better harness would help in some cases, but will achieve little all by itself. A roll cage might help in a few cases, too, but would be much less effective per pound.
Your observation is correct: Race car drivers enjoy a lot more protection than GA pilots. This is a rather recent development; 30 years ago the chances of surviving a crash were equally low for both. However, while car crashes involve mostly horizontal accelerations, airplane crashes might show accelerations from all sides. Simply put: Car drivers need protection mostly in one direction while the same protection will help GA pilots and occupants only in some cases.
There are two factors which stand out in a GA crash:

Peak accelerations which will lead to internal lesions like the rupture of the coronary blood vessels, and
Physical injury by sharp objects entering the occupant's space, including flailing limbs being hurt by sharp objects in the cabin.

Both factors were also killers for race car drivers, and they were defused with improved design methods. A safety cage is not just a frame around the driver: Any structural failure must occur in such a way that the structure fails away from the driver. In addition, the whole car body is designed to crumple at roughly the same force over its length in order to use the available crumpling zone as well as possible. This allows to decelerate the safety cage at a constant rate, so that peak loads can be avoided. A third factor is a much better restraint system, of which the HANS device is only one aspect. Using five-point harnesses would already help to avoid "submarining", a process where the pelvis slides under the lower restraint, causing the harness to press against the intestines. The image below shows the regular pelvis location and body contours as a dashed outline and the displaced pelvis and spine as a solid line. The displaced body is the shaded area.

None of this was considered at the time when today's GA aircraft were developed and the regulations were set up. At that time the prevailing opinion was that nothing could be done in a crash, so all efforts focussed on avoiding crashes in the first place. Adding only parts of the whole protection packet will be of little help - only their combination can effectively protect the race car driver. Even the 5-point harness needs an adequate seat and properly located mounting points to be effective.
The US army has collected all research up to the early Eighties in a five volume work called the Army Aircraft Crash Survival Guide (pdf!). It's intention is to improve the crash survivability for helicopter occupants and Army aviators, and much can be transferred to General Aviation. If you look for hard stats, you will find at least lots of citations there. I remember in particular a study from the Fifties where statistics showed that J-3 pilots would mostly be killed in a crash, while the rear occupant would show only minor injuries. In the study, Pipers filled with test dummies were put on rails and crashed into an earth wall. Funny stuff.

A J-3 in Army livery. Then it was called O-59 or L-4.

Any chance that you could expand on how some of the militaries studies might be applied to GA aircraft?  Would even adopting part of the race cars safety devices help?  (Like better mountings for seats so a 5 point harness would be held in place?)

@JayCarr: A 5- or 6-point harness plus a proper seat would help a lot in some crashes. But giving a GA pilot the same protection that a race car driver enjoys will be impossible: The maximum speeds and the practical limits on restraints make GA flying inherently less protectable. Regarding the studies: The guide contains a lot of excellent design advice. If heeded, GA aircraft could be much better already.

Right, I wasn't completely clear in my question I suppose.  To me it's not an "all or nothing" deal.  If any part would be helpful (without making flying impractical from a physical perspective), I'd love to hear about it.  Hence why I'm asking if you could detail the study a bit in your answer :).  (Especially since that document is veeeeery long...)

@JayCarr: It's veeeeery long for a reason: There is a lot of ground to cover. Before you can decide what to change you need to understand what the human body can endure (a lot, you'll be surprised) and what must be avoided (like sharp deceleration peaks). And then you need specific measures for all likely crash scenarios. Shaping. Materials. Procedures. And then you need to test it. All that is covered. My answers are too long for my taste already; maybe it is better to go into details in a new answer, to a new question.

It might be useful to note, in stark contrast to racing cars and even everyday passenger cars, GA aircraft have much longer service lives; not counting restored or preserved historical airframes, it's fairly common to see a serviceable 172 built in the 60s or 70s, contemporary to the Hunt/Lauda rivalry. The plane will likely have been retrofit several times in its life, but many of the safety considerations inherent in modern racing cars can't just be bolted in like a new instrument panel, and others are designed around the mentality that the car will be stripped down between races anyway.

Disclaimer: I am the VP at HANS Performance Products, makers of the HANS device. I know a little about cockpit safety but am new to the field of GA safety.
Drivers survive horrific crashes in auto racing because they are extremely well contained. A 360-degree surround seat (often called a full containment or halo seat), a multi-point harness, fireproof suit, gloves and shoes plus a helmet and head restraint are used to contain the driver. This often results in drivers surviving 100g impacts (not the 10g mentioned above). For example Ritchie Hearn hit the concrete wall at Indy at 129g and suffered only a broken foot. He was wearing a HANS device.
Although many race cars can exceed 250mph it is the rate of deceleration that causes injury. In this I think GA and auto racing accidents are similar. In fact EMT crews often talk about high speed racing accidents as airplane accidents on the ground.
There is no single magic bullet to cockpit safety. Here is a short video on the topic that may be useful to GA pilots and engineers.

The short answer is no. But if you are curious as to what it would look like check this out.
Racing accidents are generally different than GA accidents. Although race cars often slam straight into things they tend to have what is called an Impact attenuater out front. Since F1 cars are mid engine the nose is often left empty and can house impact absorbent materials. Planes are limited in this by having a propeller out front (unless its a small twin).
Roll cages in cars help to protect against (lets not be silly here) but rolling, something that F1 cars can do if they say, corner to hard and fly off the track. The thing to remember here as well is that a car only really moves in the X-Y plane. It is easier to predict how a car will and can hit something by limiting the range of motion. A plane can hit the ground at almost any attitude in any configuration in the X-Y-Z plane. This means the cage would have to be much more through. Keep in mind as well that a roll cage in a car just protects the driver, not the whole car. While you could have a roll cage just around the area that people are sitting you still have a weight issue.
Lets ignore the weight for a minute and think about when a roll cage could help a plane. If you were coming in for an engine out approach and something happened at a low altitude causing the plane to hit the ground and roll you may see some benefit. If you botch (and lets hope you never do) a landing you may see some benefit if the plane rolls over or hits something.
When it wont help, any kind of nose dive situation or sever ground impact its not going to get you much but it will get you something. In this case you want something that will absorb the shock not stay intact and transfer it to you.
It has been brought up that auto racers also wear things like wrist restraints, neck braces, helmets and harnesses. Having worn these things before I can confidently say that it is very difficult to move around in them but when driving a race car you only really need to see straight in front of you and a bit off to each side. Flying VFR would be tough if you were that strapped in and had to move your head around to look out the window.
While we are on the topic (although a bit unrelated) a fire retardant suit like the ones worn by F1 drivers could provide some protection in certain aviation style accidents as they do provide a very real, very measurable amount of protection. The best example I can think of is a serious cabin fire that somehow exists in such a way you still have control over the plane. In this case the suit may buy you enough time to get the plane on the ground and egress safely.
The real issue also comes down to cost. Are you willing to sacrifice 80-150LBS of useful load to tote around a cage that is not really going to make anything that much safer. Carbon composite shows a lot of promise in this field by simply making stronger and lighter frames but for what its worth these things are still not cheap. And lets be honest there are lots of things, like full air frame chutes, individual parachutes etc, that would make flying safer, but at some point you have to assume some risk to successfully partake in the activity.
EDIT
After some research I found out that Mooney implements a roll cage of sorts into its design see this article for some notes on it. This video claims that the newer Mooney has a "NASCAR designed roll cage to keep the occupants safe. This Thread brings up some interesting points on roll cages and reenforced structures vs the Cirrus full fame chute and may be worth a read. Although Mooney does have a roll cage of sorts my previous points still hold true in respect to ADDING a roll cage. The Mooney cage is part of the airframe its self and is there from day one of design.

Hadn't even thought of the movement restrictions and how that might not work so well for VFR v. racing a car...  Good point.

And also with regard to the weight, if you add anywhere near 80-150 lbs, you basically are killing any value of most light single engine aircraft, since they often have fairly low useful loads.

something about "X-Y-Z plane" doesn't sit well with me... space maybe?

A HANS device seems like it would be a non-starter because pilots need to be able to move their head during normal flight. Unlike race car drivers, pilots are concerned with more than just what is directly in front of them or to their left. Also, they need to be able to grab stuff out of the back, adjust radios on the other side of the cockpit, etc.
In most cases, a GA aircraft 'crash' will be less violent (i.e. lower instantaneous acceleration) than a car slamming into another car or a wall. While this isn't always the case, in most cases a crash is either just sliding off the side of a runway or landing on something that isn't meant to be landed on, not usually impacting something head-on. Additionally, aircraft generally don't roll. They might flip forwards over the nose, but rolling is rather difficult, given the length of the wings. The wings would usually have to break off or the roll would have to happen while airborne and then crash inverted in order for the aircraft to 'roll.' As such, the added weight of the roll cage would generally not be worthwhile, especially since it would be a very significant portion of the overall weight in a light aircraft, which matters a lot more than the weight of a car.
As far as more complicated restraints, they would have to be very quickly and very reliably removable. Fires are a big issue in light GA crashes, so the ability to get out ASAP is very important.
As far as helmets are concerned, while these might make sense in aircraft that are operating in conditions where a crash is more likely (racing, aerobatics, etc.,) it seems like their annoyance in normal use would outweigh the benefit in the still rather unlikely scenario of a crash. Even from a pure safety standpoint, annoying/restricting/distracting the pilot seems likely to cause more fatal accidents than it would prevent. In general, I'd say the reasons are pretty similar to why we don't wear helmets when driving down the highway, even though my car will be moving faster on the drive home from the airport than my plane will be moving on touchdown. The cost/benefit ratio is just too high for it to be worthwhile.

Most race cars actually turn right, too, but your point is still valid. ;)

Additionally, most, if not all race series have driver escape rules that state that a driver must be able to release the safety restraints and get himself out of the vehicle in a matter of seconds (5 in F1, I'm sure it's similar in other series).  All in all, your points are very valid. I'm just nit-picking.

Most race-car crashes occur when there are safety crews on hand who can assist in extrication and can attend to any fires within a small fraction of a minute.  I doubt that's true of GA crashes.

@supercat, generally true, however, I've seen accidents where another driver was out of his car helping someone out long (30+ seconds) before any of the track crew were there to help. Of course, even if the crew gets there within 1 minute, that's significantly quicker than your general fire-fighting crew will get to the scene of an off-airport* airplane crash. *On-airport, with a call before your crash landing will have the crews on standby at the side of the runway...

@FreeMan That's only true if you know you're going to crash well ahead of time, which is usually not the case with GA. It would apply to a gear extension failure or something of that sort, but not to most incidents. GA airports don't have fire crews on site like the big airports do. If you call, say, an engine-out landing, you'll almost certainly arrive at the airport way before the fire crew unless there happens to be a fire station next door to the airport.

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text:
Are planes assigned different climb angles from the airport by the tower?
Clearly the angle at which planes take off and climb depends on lots of things (mountains, residential area, aircraft type, wind) but when watching planes take off after another from the same runway, I have the impression that similar aircraft climb at different angles right after another.
So I'm wondering it this is a measure to increase the distance between two planes quickly after they leave the airport? Such that every other aircraft is asked to leave flat'ish (within what the plane and regulations allow) and others more steeply?
The question occurred to me at GVA (single commercial runway).
This is about the initial climb angle, not their course heading.

I mean the angle that the planes climb at for say the first km of flight

I have proposed an edit to try to clarify that the intent of the question is the climb angle, not heading. This question is now on the hot network questions list, making a clear and unambiguous title all the more important.

There can be many reasons. Flights taking off one after another:

have different destinations
have different weight and balance
have difference in wings and wingtips
have pilots with difference in skills
got different takeoff directions by ATC
are trying to avoid wake turbulence

Off all the reasons I mentioned above, perhaps wake turbulence might be playing more role about difference in takeoff angle. There are a ton of questions about wake turbulence, which is worth a read.

Different departure headings is not a valid wake turbulence separation. We need x number of minutes between departures for wake turbulence, regardless of direction of flight.

No, planes are not assigned a specific climb angle by the tower upon takeoff -  the tower will not instruct an aircraft to "climb at FPA 4 degrees" or "climb at 1200 feet/min". Separation is achieved primarily by lateral distance.
If there is a risk of collision (e.g. an aircraft has just taken off, and the landing aircraft executes a go-around), ATC will issue a different heading to one of them.
The initial climb from the runway is hand flown by the pilot; even if conditions are the same, different pilots might have climbed the aircraft at a different angle. Besides, there are quite a few factors which will influence the initial climb you observed:

A heavier aircraft will have a higher Vr, which will delay rotation. An aircraft heading to a farther destination will carry more fuel and be heavier, even compared to another aircraft of the same type.
If the aircraft is empty (e.g. positioning flight), the pilots can probably climb faster.
If the fuselage is long (e.g. 777-300) and the pilot pitch up too much, it will have tail strike.
Company SOP may require the pilot to "pitch up to X degrees" for passenger comfort.

Referring to the takeoff pitch angle differences, they are often due to aircraft characteristics or situational things, like potential wake turbulence, or known obstacles. Planes have different speeds for best climb, and that will result in different take off angles. consider an F-18 putting out full afterburners on takeoff. That pilot could go straight up, no problem. At my flight school on the other hand, someone was training in a home-built LSA (I don't remember the type) that I swear had a max fpm climb rate in the TENS. (joking, somewhat). That little plane had to do a LONG and SLOW climb. Anytime in the pattern behind him was laughably interesting, having to extend the pattern in all sorts of ways. That was fun for a newbie trying to learn how to land in the first place.
Aside from that, departures vary for safety and often convenience, keeping planes out of trees, wake turbulence, and other planes. Planes with short takeoff rolls can usually get above obstacles (50') or wake turbulence effects before most of the runway is taken up, allowing for a shallow climb. Other planes might require more runway, leaving a steeper climb required to clear obstacles.

yes, the initial departure or approach vector is decided at least in part by the performance of the aircraft to have it intercept the first waypoint of the SID/STAR at a decent angle.

OP clarified in comments they mean vertical climb angle, not heading.

Fixed it, thanks

A climb rate/angle assignment will not be assigned, altitude only.  The standard climb rate is 200 ft/nm unless otherwise published, but ATC won't verbalize the published climb rate unless queried. The closest thing to your question would be the assignment of a departure procedure.  DP's have a required climb gradient based on the departure runway to ensure obstacle separation or satisfy noise abatement procedures.

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text:
Is communication with cabin crew or ATC included in emergency checklists?
In a serious but non-catastrophic situation on a commercial flight (for example, a single engine failure on an A320), I understand that the pilots will follow a standard checklist (from the QRH) to put the aircraft into a safe condition.
My question is - will such a checklist generally include an explicit item to inform ATC, the cabin crew, and/or the passengers, or is this generally assumed to be done as a "standard procedure"?  If it is usually on the checklist, would it always come at the end, or are there situations where ATC might need to know about the incident as soon as possible?

In the case of A320, yes it does. Here’s an example of the emergency procedure for ditching. Note there are four instances where it tells the pilot to communicate with the cabin.

Also note the ATC... NOTIFY, which answer's the second half of the OP's question. In electrical failure modes, not all radios may be available, so it serves as a guide to which radio to use.

Thanks for the information, that's just what I was looking for.  In particular, the sequencing does appear to vary depending on the nature of the incident.  I assume that the procedures are only available on a commercial basis - or is there somewhere they can be (legally) obtained publically?

@Tevildo There are copies of the FCOM and QRH out there on the net. I'm not sure exactly how legal it is for them to be out there. Airbus might consider it proprietary info. But if you do some googling you can usually find them.

The classic saying in an emergency is

Aviate
Navigate
Communicate

Fly the plane, find a field, then deal with the radios as my instructor used to say. The checklists generally only cover how to work the aircraft from an aircraft operation standpoint but may note it towards the end. Since in most cases you have two people in the cockpit CRM often results in one of the two people manning the radios. In this case the pilot flying the aircraft may work the problem as the co-pilot relays the info to ATC. However emergencies may require you to communicate as part of working the problem i.e. requesting an altitude block to work the problem. This is the actual emergency checklist I trained with the only note to contact ATC/declare is under the Time Permitting section.

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text:
Can thrust be selected manually in a plane with autothrust? If yes, how?
I'm getting into the autothrust world and I have the question of whether it would be possible to disengage it and select the thrust manually in a plane that already has autothrust. How could it be done? Maybe it differs from plane to plane.

....disengage the autothrottle and make thrust inputs using the throttles?

You are correct that different planes operate slightly differently, but they are mostly pretty similar. Just as with the autopilot, the autothrust can be disconnected and the airplane can be controlled manually.
Below is an image of the Mode Control Panel on the 737 NG, which is located just below the windshield. The section that controls autothrust is located towards the left side. To disconnect the autothrust, you can just flip the "arm" switch to off.

Source
Below is an image of a 737 NG cockpit, with the thrust levers located in the middle. With autothrust on, the levers are moved by the autoflight system to correspond to the autothrust setting. The levers can be moved by the pilots but the system will try to drive them back to the commanded position. Once autothrust is turned off, the system no longer moves the levers and they can be controlled by the pilot manually.

Source
Airbus planes such as the A320 are a bit different. The levers do not move to match the autothrust setting, but autothrust can still be turned off to use the levers manually. The levers can also be pushed forward past the "climb" detent, which overrides autothrust to choose higher thrust settings.

"The levers do not move to match the autothrust setting, but they also have specific detents that can be used to override autothrust to set certain manual thrust settings." Detents are used to set autothrust limits, not override it. Also in an Airbus, the A/T can be disconnected, and the levers work just as in any other aircraft.

@Sami from the linked post, "When the thrust levers are beyond the CLB detent, thrust is controlled manually to the thrust lever Angle." I edited the wording here a bit.

Well, goes to semantics a bit, but beyond CLB autothrust is not usable, so it's off. Anyways, it's agains airbus' SOP to use the thrust levers to override autothrust though it is possible.

On the 737, even with the autothrottles engaged, you can override the servos and move the thrust levers.  The servos will pull (or push) against you to attempt to put the throttles where they "should" be, but it isn't difficult to override them. This action does NOT disengage the A/T, although if you get tired of overriding the servos, that may become the obvious choice.


text:
What are these accelerating flare countermeasures called?
There seems to be a type of flare countermeasure, that not only gets ejected from the flare dispenser, but also gets accelerated in the direction of the plane. So fare I´ve only noticed it on super and legacy Hornets.
My question is, whether anybody knows the actual name for those kinds of flares, and if there is any kind of information on how they work.
Video of legacy Hornet dispensing a normal and an accelerating flare
On the left Hornet you can see one of the two flares accelerating forward in a spiral after it is out of the dispenser.
Video of super Hornet dispensing a normal and an accelerating flare

These are generally called "propelled flares", or sometimes "aerodynamic propelled flares". Some antiaircraft systems are able to distinguish between a normal flare and the aircraft, as the flare is not travelling along the expected path of the aircraft. Aerodynamic flares were first developed to allow the flare to continue along the path, but as antiaircraft systems developed further, they added a method of propulsion (which uses the same fuel source as the flare itself), to ensure that the flare continued alongside the aircraft, slightly angled away, at a similar speed. This does a better job of confusing these aircraft systems, but it's a fairly "niche" type of flare that is meant to combat conical scanning.
I believe the ARM-031, MJU-47/B, and MJU-71/B are all forms of propelled flares.


text:
How often is a tire replaced on a 777?
Given that it is long haul aircraft, and is most widely used by airlines in that capacity:

How often do they replace the whole tire?
How much does 1 tire cost the airline?

Aircraft tires are replaced on condition, but maingear tires usually last about 250 cycles. A 777 in longhaul usage might only get two cycles a day, so a set of tires would last about four months.
The 777 uses a 50x20.0r22 with 32ply rating. I couldn't find that exact tire but a similar one costs $4700 new. It is common practice to retread or remold worn tires after inspecting the carcass to ensure its serviceability, and these cost about half of new.
Interestingly, this study by Embry-Riddle suggests that 99% of tire wear could be eliminated by prespinning the tires prior to touchdown, eliminating the puff of smoke you see as a part of the tire burns away as it matches up to relative runway speed. If correct, a tire would effectively last forever, until it was damaged as by debris or a hard landing.

Here's more information about pre-spinning tires before landing.

Very informative. Appreciate the detailed response!

That's about half the price of a tire for a Bugatti Veyron.


text:
Why does idling RPM increase with altitude in a jet engine?
The Snecma-Larzac 04-C6 idling RPM ranges from approximately 53% on the ground to 85% at high altitude. Why is that?

For one there is less resistance to the fan and compressor due to the decreased air density -> more rpm out of the given power. On the other hand, the mass flow needs to be high enough to sustain the operation of the engine -> both lead to a higher rpm...

There is also the ram air effect in flight at altitude.

Ground idle and in-fight idle are different.  In-flight idle would move aircraft on the ground and would require a bit of brakes to keep the aircraft stationary. Additionally, landing roll would be longer. Therefore, ground idle activates on most jet aircrafts after touchdown. This activation is usually occurs after a small delay, taking into account that pilot may be doing a touch and go.
Of course there is also density effect on both ground and in-flight idle rpms. Both increase with altitude to provide some engine stall margin.

Would "ground idle" be different for an airfield at MSL vs one at MSL + 5000'?


text:
Can TCAS give an RA for one aircraft and a TA for another?
I am an air traffic controller and I had the following situation. Traffic maintaining FL360 and below him traffic at FL350 requesting FL370. Once they crossed each other I gave clearance to climb FL370 with 5.1 nmi separation. The guy read back the clearance and said he received a TCAS RA, the guy at FL360 said he received a TCAS TA. Does this make sense?

I am an ATCo as well, I have never seen, controlled, faced any similar situation before.

Without knowing the geometry (opposing, crossing, in-trail) of the encounter, whether there were other aircraft in the vicinity, when the RA/TA occurred, and what the RA guidance was; it would be hard to say whether it made sense or not.  Normally, an RA between 2 TCAS equipped a/c will be coordinated and exist for both.  The RA may have been for another a/c (and he didn't report it as it was a 'Maintain' and did not have to take any action).

It is very strange other traffic were away from those 2 aircrafts might TCAS system has messed up.anyway I filled report waiting for the results.thanks guys.

Normally TCAS RA for one, means RA for the other one as well unless the later has set is system to TA only and forgot to set it back to TA/RA.

What kind of aircraft were they?

Aircrafts involved B777 received TA & B737 received RA

See also Can you have TCAS RA if your other traffic only have TCAS TA?

It's hard to give a definitive answer without more information.  My go-to for TCAS details is the FAA's Intro to TCAS II. In general, an RA will try to coordinate with the other aircraft, but such coordination doesn't require the other aircraft also issue an RA, it only listens for other RA "intent" messages and makes sure it doesn't issue a conflicting RA.
Here's some possibilities:

A marginal RA encounter.  Each airplane has slight differences in calculation , so, as the FAA manual linked above reads, "In a majority of the TCAS/TCAS encounters, the two aircraft will declare the other aircraft to be a threat at slightly different times"
The TCAS of one aircraft was set to TA-ONLY, although this normally only happens if the airspace is busy
One had an inaccurate pressure altimeter reading
Thresholds are larger at higher altitudes and this could have contributed to the higher altitude pilot receiving only a TA
One airplane was running TCAS I instead of TCAS II and couldn't get RA's.  This is probably not the case if the aircraft was commercial.
They're running different versions of TCAS with slightly different algorithms

Good answer, although third point I disagree with. Whatever altitude the TCAS thinks it's at, is what it's going to use. If it's wrong (i.e. they're at FL352 not 350 as shown, or vice versa), the indications will be something other than they ought to be, but each aircraft has its singular altitude that the system is working with. (My bet would be that your second point is what happened -- TA Only set when TA/RA was intended. Just my guess, though.)


text:
Aviation terminology for 'in the field'
I'm writing a sci-fi story involving aircraft and space craft. I'm struggling to get the terminology right for referring to a pilot being 'in the field' either on a mission or a training exercise. I have a feeling there is a phrase for this but I'm struggling to think of it.

Gotcha. I was wondering whether or not this was the best place, actually. I didn't know about the Aviation StackExchange. Thanks.

@sphennings: I figured creating appropriate lingo for my characters fell under this topic. But yes, I see your point.


text:
Is this "wing-wave" early after takeoff really a pilot tradition?
I saw this video of a "wing-wave" immediately after takeoff of a 747-8 pop up on my Instagram feed. In the description, someone says that their friend is the pilot and that he did it to wave goodbye as it was the planes last visit to the airfield and that this is a tradition among pilots.
To the layman like me, it doesn't look too safe - but since the pilot did it, I'm sure it is. Is this really a pilot tradition and do they do this on passenger flights and most importantly, was this safe?
A comment (for what it is worth) said:

Steep banking an aeroplane few seconds after rotation at dangerously low speed and low altitude is always dangerous. Waving goodbye is not uncommon however this would be considered reckless. I would not be surprised if his competent authority and Company would have an issue with this.

It does seem a little low to start that maneuver, however the aircraft is moving a lot faster than it seems because of the camera zoom


text:
Are tritium runway lights widespread in remote areas?
There was some interest in the 80s and 90s in providing runways in remote areas with tritium lighting (which requires no external power, since the radioactive decay in a sample of tritium gas induces radioluminescence in a suitable material). However, apart from this failed trial in Alaska (pdf) and various vague mentions of it on the internet, I can't establish if this every became a viable technology.
Has it become widely-used (perhaps for military airstrips, if not for civilian ones)? And if so, how did the technology improve in the last couple of decades to make it work?

Good question, but I think the fact that you cannot find any references beyond the failed trial points towards a negative answer. Would still be nice to hear from someone who has had experience with alternate lighting systems.

The document you posted said that Tritium lighting was in use in Alaska for part 91 operations at the time, and was FAA approved for that, document was for testing approval to part 135 operations.

I would think the advent of solar/battery powered LED based systems, along with really effective reflector based systems, has killed whatever market interest there would be in a tritium based system.

I would hope, @JohnK, that they use a better solar panel/battery combo than the ones on my back deck lights! ;)

Some poorly funded GA airports had/have reflectors in place of lights along the runway. Your landing light made them show up fairly well.  Some runways had radar reflectors on the approach end of the runway (mostly military, I assume.)

I think it's a major headache to heave radioactive material in remote areas. Soviet union used RTG for lighthouses. A lot of countries were worried about that. You can find articles on the internet. So probably it's not very good idea due to threats.

Tritium has a very long half life and a simple decay chain which produces no neutrons.  Also, it does not bioaccumulate.  It is much safer than an RTG.

One RTG per light would be way too much power.  A runway doesn't need a frickin' laser^H^H^H^H^H lighthouse every fifty feet down the centerline.


text:
Which airline will get me from Paris or London, to Japan, and has a zero fatality rate?
I only fly with airlines with a zero fatality rate (it helps my fear of flying, yes it might not be logical, I know:)… but have so far only travelled around Europe and to Africa with Easyjet and Ryan Air.
Now I want to go to Japan (from either Paris or London).
Is there an option for me?

The chance of you being the first is still non zero though.

I have proposed an edit based on the fact that OP accepted an answer talking about airlines, not airliners.

That said, wouldn't this be a much better fit on [travel.se]?

Please remember the be nice policy, and assume good intention. The comment of yours ive deleted was not very nice considering someone was trying to point you to a (potentially) better place to answer your question.

Note that the fatality rate for 2017 for all airlines worldwide was zero.

@ymb1. Given the question has 3 tags that are relevant it would appear to be very much on topic?  It's a question about aviation safety, of which there are 650 in aviation stack exchange. And it's been given a good answer.

@Cloud "people like to close questions for fun" Look at What topics can I ask about here? in the [help]. One of the bullet points about questions that are off topic is specifically "passenger aspects" of commercial air travel. It doesn't really make more sense to ask a pilot, aircraft mechanic or air traffic controller about on which airline to book a ticket, than it does to ask a travel agent about the finer points of aircraft jet engine design or the aerodynamic properties of an autogyro. They might know, but it's not their job.

@MichaelKjörling Given the question has 3 tags that are relevant it would appear to be very much on topic? It's a question about aviation safety, of which there are 650 in aviation stack exchange. And it's been given a good answer

@Cloud - If 3+ of our highest rep users think its off-topic then guess what... it's off topic. Just copying a misguided comment from someone else doesnt change that. Not all aviation safety questions are on-topic, this being one of them.

@Jamiec.  I agree, not all aviation safety questions may be on-topic.  If he'd just asked for the cheapest ticket, it would be a question just about the "passenger" aspect of travel. But he asked about the safest. Safety is a technical aspect. The list of topics given in the help centre isn't very broad at all. For example, jet engines aren't mentioned at all, yet there are 450 questions about them. So, if a question can link to 3 tags that are relevant, it does beg the question how it's off topic? Or are you saying the tags are not relevant?

Qantas to Singapore, onwards to Japan with Jetstar, also owned by Qantas.
From this Wikipedia article:

In 2014, Qantas was rated the world's safest airline by Airline Ratings.

Rainman already knew..

For jet transport, Qantas is a zero-fatality-rate airline, has been for over 50 years, flying some of the longest distance air services in the world. The flying boats during wartime are a long time behind us.

Thanks so much! I'm guessing there is no direct route?

@Cloud unfortunately not.

Another option is KLM, they've not had an accident since 1981 and that one was due to a freak weather phenomenon that nobody could have foreseen snapping off the wing of a brand new aircraft like it was made of tissue paper (technically it wasn't even KLM, it was a regional subsidiary, the last mainline accident they had was Tenerife in 1977 over 40 years ago).
They'd probably get you there faster than Qantas too, as you'd be changing planes in Amsterdam rather than having to take a major detour to Australia.

Thanks for this, do you have links to the pages of those accidents, sounds interesting.

@Cloud I suspect that'd be KLM Flight 4805 in 1977. You can start at the Wikipedia page on the Tenerife airport disaster, then follow its citations.

Qantas flies London- Singapore.

@Cloud that's the one. Before that the last fatalities in KLM flights I know about were on a Constellation that crashed on takeoff from Shannon somewhere in the 1950s. The 1981 crash was an NLM Cityhopper (now KLM Cityhopper but an independent airline owned by KLM at the time) Fokker 28 https://en.wikipedia.org/wiki/NLM_CityHopper_Flight_431

Saying that KLM has had no accidents since 1981 might make the asker more comfortable with KLM, but that comfort is probably completely undone by then immediately describing the 1981 accident in graphic detail. "New Aircraft Wings Like Tissue Paper" is the headline I'm left with.

@ToddWilcox well, the weather conditions were such that no aircraft would have survived them... And it was a fully owned subsidiary, not the main company


text:
What is the maximum speed of the Cessna Citation X?
What is the maximum speed of the Cessna Citation X?
I want to attempt to break the sound barrier but I do not know if its possible, where, or how to do it.

If you want to break the sound barrier, there are a number of places you can go to buy rides in ex-military aircraft more than capable of doing it without breaking apart. Would be much cheaper than buying a Citation X and having the insurance company deny the claim (not that you'd be there to contest it anyway).

A better candidate for what you're asking about might be the G650. Published MMO is 0.925, with rumors of flight tests beyond 1.0 that were no big deal. May be problematc to get somebody to just lend you one for a joyride, though. I've heard the Russians will sell you a MiG-25 ride for the right price, so that may be your best bet.

If you just want to break the sound barrier then an ex-military jet of some kind is probably the simplest way. If you have EUR 11,500 then these guys will take you in a MiG-29, for example. And as a general comment, I suggest that before posting questions you consider exactly what you want to know, e.g. do you want to know the maximum airspeed of a Citation X, or do you want to know where/how you can break the sound barrier? Those are completely different questions.

@TomMcW eh, I'd find a better example, those damages were due to the excessive g-loads.

If you want to do it, become a test pilot and then you will be allowed to fly the Citation X a bit above MMO. The safety margin until flutter or Mach tuck will kill you should allow to go supersonic. But once you are a test pilot I am sure you will see the silliness of that particular concept.

@PascalAckermann To my knowledge Cessna no longer lists specifications for the out-of-production Citation X, only for the Citation X+. Are you sure you were looking at information for the Citation X (S/Ns up through 75-0500)? Don't mistake the Citation X+ speed specifications listed on Wikipedia and Cessna's website for the Citation X. They are different. See the TCDS. And tell me a novice should be able to interpret a TCDS.

No, they still sell it.  I am a pilot and I see them in airports.  I also fly them.

@DanielChung Oh, fly the Citation X, do you? Cessna may still sell the Citation X, but all new production has moved to the Citation X+.

The Cessna Citation X has a maximum speed limitation of 0.92 Mach.
The following limitations apply to the Cessna Citation X, serial numbers 750-0001 through 750-0500:

Below 8000 ft., the maximum operating speed (Vmo) is 270 KIAS.
Between 8000 ft. and 30650 ft., the maximum operating speed (Vmo) is 350 KIAS.
Above 30650 ft., the maximum operating speed (Mmo) is 0.92 Mach.

The Cessna Citation X+ has a maximum speed limitation of 0.935 Mach.
The following limitations apply to the Cessna Citation X+, serial numbers 750-0501 and on:

Below 8000 ft., the maximum operating speed (Vmo) is 270 KIAS.
Between 8000 ft. and 31500 ft., the maximum operating speed (Vmo) is 350 KIAS.
Above 31500 ft., the maximum operating speed (Mmo) is 0.92 Mach.

All information above is cited from the Cessna Model 750 type certificate number T00007WI.

While the Citation X+ is currently the fastest production civil aircraft, its top speed at altitude is still a little below the the speed of sound. At lower altitudes, the speed limitations are even more restrictive, keeping the aircraft well below the local speed of sound.
The speed of sound is expressed as Mach 1.0. The Citation X is limited to Mach 0.92 and the Citation X+ is limited to Mach 0.935. This means that neither of the Citation X series aircraft are allowed to be flown at or beyond the speed of sound.
The limitations for the Citation X series of aircraft prohibit flight at or above the speed of sound, Mach 1.0. Attempts to do so are generally against regulation, reckless, and ill advised.

The Citation X maximum speed is Mach 0.935.
You could have gleaned this information from the Wikipedia page, which you are obviously familiar with from your other questions.
What this has to do with breaking the sound barrier is entirely unclear. The Citation X is not the aircraft to do it with, but if you have funds I'm sure you could find a privately owned warbird that is designed for it and a pilot/owner who'll oblige you.

Wikipedia has an incorrect figure. The Mmo of Citation X is 0.92 M. The 0.935  figure is for Citation X+

From Cessna Citation X:

Maximum speed: Mach .935 (MMO)

So, no. Exceeding the maximum rated speed in that aircraft would be highly inadvisable. More generally, so would attempting to exceed the sound barrier in any aircraft that is not specifically designed to do so.

Would the plane shake or something and could I do at sea level where the sound barrier is lower?

@DanielChung I don't know exactly what you mean by the sound barrier being lower at sea level, but note that the speed of sound is higher in denser materials and slower in less dense material. In other words the speed of sound is higher at sea level and lower at 30,000 ft.

@DanielChung The maximum speed is expressed in the local speed of sound (Mach number), not relative to the speed of sound at sea level. The aircraft is physically limited due to supersonic effects, not to a certain true air speed.

As mentioned in many of the previous answers, The Cessna Citation X (Mach 0.92) and X+ (Mach 0.935) are fast, but not fast enough to go rattling windows at altitude.
Breaking the sound barrier sans concord service can still be done and I’ve seen quite a few answers here that I believe are correct, but a bit expensive.
Assuming you aren’t in the top 1%, there might be another option to at least get you in a jet that’s fully capable of Mach 1+, and the best part is the price: $0.00.
The United States Airforce has an image to maintain and it loves to create as many cheerleaders as possible with different outreach programs, air shows, the Blue Angeles flying over the Super Bowl, etc…
There are two additional ways I’m aware of that might have you joining the supersonic club:

A pilot can request that you be permitted to go up with him on a flight. I don’t know if these are granted or requested often. It’s the kind of thing people sometimes get to do as a reward for something like saving a Airforce Generals kid from a burning building or catching a terrorist. Also, If some reporter is on the scene and asks if you’d like anything in return, don’t be shy. Let them know that you want to go like Chuck Yeager.

Become a Key Influencer or get press credentials. This is much safer and probably your best bet. I’d probably try starting a YouTube channel about all the cool stuff the Airforce does and hope the followers start subscribing. I’d think that + a high ranking officer as fried, and you’d be in the money!

I’d also tell every member of the Airforce, Navy, and Marines, that your dream in life is to go Mach 1. I’ve been amazed at some of the things I’ve gotten to do just by asking politely. But, my requests are usually subsonic or sexual in nature.
Note: To my knowledge It is illegal to exceed Mach 1 above the continental United States. (Nevada may have an exception for the huge test area.) So, if you get to go on one of these rides, make damn sure you you’re on the coast and flying over the ocean. If you fly out of Dallas Love field or something, you’re going to get a subsonic only joyride. If that pilot exceeds the speed of sound above a populated area just because you want to, it will be his last time operating any jet owned by the DOD.

The Blue Angels are the Navy Flight Demonstration Team.  The Air Force team is called The Thunderbirds.


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What is this fighter-like plane with huge wings?
Can anyone identify this strange plane? It looks like they took wings from a bomber and put them on a fighter body...
What was its purpose?

The body is not from a fighter, but from the EE. Canberra high-altitude bomber (which already had a pretty big wing to begin with)

@Hobbes remember the size of aeroplanes has increased dramatically since the 1950s - the EE Canberra had a length of just under 20m, while todays fighters have similar lengths - both the F-15 and the F-22 have a length of roughly 19m.

The Martin/General Dynamics RB-57F Canberra is a reconnaissance aircraft.
The RB-57F was derived from the Martin B-57 Canberra, a tactical bomber and reconnaissance aircraft built on license from the British English Electric company. With its enlarged wings and more powerful engines, the RB-57F gained extreme altitude capabilities. It can climb up to 24,000 m (80,000 ft). It was developed and built for the US Air Force. The first flight was in June 1963.
900 British and 49 Australian Canberras were built. 403 American B-57s have been produced, of which 21 have been converted to RB-57F. Some aircraft were operated by the air forces of Pakistan and Taiwan. Two RB-57F crashed on USA territory, and one aircraft was lost over the Baltic Sea. Only a few aircraft have been salvaged. Most of the RB-57Fs ended up at the AMARC bone yard (source).
The particular aircraft on the question's picture with serial number 63-13291, was converted from a B-57 in 1964 and served the US Air Force till 1974, when it was put into storage at the AMARC bone yard.

picture source: NASA (https://acd-ext.gsfc.nasa.gov/People/Newman/wb57_pics.html)

picture source: NASA (https://airbornescience.nasa.gov/gallery/aircraft/WB-57_-_JSC)
Today there are still 3 planes (now called WB-57) in service for the NASA Airborne Science Program.
There is a Wikipedia article about this type.

Thanks! Interesting that (almost) everyone is familiar with the U-2 and SR-71, but probably far less people have heard about this aircraft. Probably due to the far less "glamorous" reconnaisance missions (no spying on the Soviets) and the very short service life with the USAF (only ~10 years). But very interesting trivia also: 3 of the planes are still flying, and "NASA 927 now holds the distinction of being the aircraft held the longest time (41 years) in extended storage before being returned to flight status"...

Near the end of the shuttle program, they used these planes to obtain tracking imagery for shuttle launches.  The cameras on these guys (located in a rotating turret on the nose) have ridiculous optics and can pick out extremely clean detail from miles away.  These planes also have a very distinct sound when they fly overhead (they frequently fly out of Ellington airport, near my house).

Just thought I'd link a post about them! https://arstechnica.com/science/2018/11/three-high-flying-birds-soar-together-for-the-first-time-since-the-1970s/

The base plane is an ENGLISH ELECTRIC Canberra.

Sure, but that's already been mentioned in the answer.


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What is this small black rubber strip protruding out of the flap track fairing of the A320?
On the Airbus A320 wing there in whilst in flight a small black rubber strip protruding out of the flap track fairing. What is it please?

It appears to be one of the rubber seals that are on the moveable flap track fairing.

source
Since the fairing moves away from the wing it has probably come loose and is caught between the fairing and the flap.
I can't find a good photo of a fairing from an A320, but here is a photo of the fixed fairing from an A350. It's hard to tell if they are exactly the same, but you can see that they look similar.

source

I am a real world pilot and flying the A320 Family. The little black tube there isn't visible normally, but it looks like the main holders and calmer gum between the wing and movable equipment (Flaps, Spoilers, ...).

You can see the black stripe at the right wing outer flap track fairing!

Welcome to Aviation.SE!


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Where can I find blueprints for the Wright Model HS?
I'm looking for the Wright Model HS blueprints. Can someone help me?

You may want to reach out to the national archives they seem to have at least some of the Wright Brothers Blueprints. The Smithsonian may also be of help as they seem to have some stuff of theirs as well. This organization also has some of their early plans and seems to be knowledgeable on the topic you may want to reach out to them.


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Where can I obtain official German VFR approach charts?
I am looking for the official VFR approach charts of German airports. I could found a preview here : airports.de however I do not know where I can find the official ones or where I can order them. This would be useful to purchase the  maps only for the  airports I am interested. Any suggestion?

Happy new year all you passionate aviators ,
Yesss!!! The time is here. All German VFR charts are available for free now. Here’s a link to the German VFR AIP. Look under AD for all VFR charts for all airports:
https://aip.dfs.de/basicVFR

thanks a lot !!! Amazing!

Don't know what this will bring or what to expect, but I found this notification today:
The Aeronautical Information Publication Germany (AIP) can be used free of charge from January 2023. An online version can then be accessed via the AIS-Portal of DFS.
For several years now, DFS has made the current version of the Aeronautical Information Publication (AIP) available free of charge via its aeronautical information services portal at www.dfs-ais.de. The German Aeronautical Publication Agency, as publisher of the AIP, will also be making the supplementary volume AIP VFR available in a free version on the AIS-Portal from January 2023.
This will provide all airspace users, whether they are flying IFR or VFR, with easy and free access to the AIP. The two Aeronautical Information Publications (AIP IFR and AIP VFR) will continue to be distributed in the usual form via the online shop of the DFS subsidiary R. Eisenschmidt GmbH.
Link to the website.

Welcome to the Aviation Stack. This is a great answer to this question. I hope the OP comes back to recognize this contribution!

Amazing answer ! thanks a lot

The official German AIP VFR is only distributed via a company called Eisenschmidt. I'm not even sure, there's a digital version of the official charts. But you can buy a 2.35kg heavy print version of the VFR AIP. The only thing that comes close to the charts digitally is something called "VFR eBulletin", a software, where you can enter your route and see that overlaying an ICAO map - but the map is in very bad resolution and low quality.
Sadly, Germany doesn't do it like many other European countries by publishing their AIP VFR online for free.

There is a little hope with Foreflight for EU. Apparently they plan on putting the Jeppesen database in their and hopefully also the charts.

http://ww1.jeppesen.com/index.jsp  approach/aviation for charts worldwide.  A paid subscription to a service is usually needed.  That's what the airlines use.  Jeppesen has been in business a long time. Official enough for me. Does Germany have FAA Approach Procedures like the US does? That could be searched for at Germany FAA equivalent websites. Here's the link to US charts to give you an idea of what to look for. faa.gov/air_traffic/flight_info/aeronav/digital_products/dtpp

But do those count as "the official" ones?

While your points are valid, you should include that information in your answer up front to explain who Jeppesen is and how someone could find official charts there, rather than having to leave comments later.

I agree Jeppesen covers them, but I would be more interested by the official one. I know that in France there is an official website for all VFR charts


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Why can’t takeoff rejection be automated?
According to this comment on my previous question about automatic instrument takeoffs (or, rather, the lack thereof), the reason takeoffs are always flown manually is to allow the pilot to quickly reject the takeoff if necessary:

A failure, like a tire blowing or engine fire requires pilot intervention immediately. It would be better if the pilot as at the controls when it happened rather than having to disengage the automatic systems and play "catch up" with flying the plane. I'm sure this will get there at some point, but right now it's just better to have your hands on the controls and mind in the game during this critical phase.

What I don’t get is why a takeoff would have to be manually rejected - an autopilot can react far more quickly than any human pilot could ever hope to do; applying the brakes, deploying the speedbrakes, and idling and then reversing the engines are all actions that could easily be automated (and, in fact, the first two already are, not least for this very reason); and, of the many reasons for rejecting a takeoff, all suggest avenues for automation.
For instance:

Engine failure - Have the autopilot continuously monitor engine parameters, and do an RTO if one engine fails prior to V1, or if multiple engines fail at any point during takeoff.
Flight control failure - Have the autopilot continuously compare commanded to actual control surface position, and do an RTO if, at any point during the takeoff, one or more control surfaces fails to move when commanded, moves an insufficient amount, or moves in the wrong direction, or if one or more control surfaces moves when not commanded.  Also have the autopilot continuously monitor pressure in all hydraulic systems (for aircraft so equipped), and do an RTO if a partial hydraulic failure (or, for aircraft with manual-reversion capability, even a total hydraulic failure) occurs prior to V1, or if an aircraft without manual-reversion capability suffers a total hydraulic failure at any point during the takeoff.
Pitot-static failure - Have the autopilot continuously monitor the altimeter and airspeed indicator readings, and do an RTO if the altimeter readings disagree (within a certain tolerance) with each other and/or with the runway elevation (for instance, if your altimeter says your altitude is 3 kft MSL on the runway at Amsterdam Schiphol, or reads 0 ft MSL in Mexico City, either someone royally screwed up the altimeter setting, or your pitot-static system is malfunctioning; either way, an RTO is warranted), if the airspeed indicators disagree with each other (again, within a certain tolerance), or if one or both airspeed indicators fail to come alive within a reasonable time.
Et cetera - Et cetera, et cetera.

None of this would require the use of any instrumentation not already in place, little if any modification of the autopilot (other than the software update necessary to program the rejected-takeoff routines into it), or of what it can control, would be necessary, and automating rejected takeoffs would considerably increase operational capabilities (since, firstly, the quicker reaction time of an autopilot versus a human pilot would decrease the time needed to initiate a rejected takeoff, thus shortening the timespan from when the rejected takeoff is commanded until the aircraft comes to a halt, thus shortening the distance needed for a rejected takeoff, thus shortening the runway length required for a given aircraft at a given weight with given atmospheric conditions, thus allowing the aircraft to operate from shorter runways, and/or from runways at higher altitudes, and/or at heavier weights, and/or during hotter and/or humider weather; and, secondly, because adding autoRTO capability would remove the final obstacle to automated instrument takeoffs, which would allow safe takeoffs in much lower, or even zero, visibility, which would - in the same vein as ILS-guided autolanding - greatly ease foul-weather operations) and safety (due, firstly, to the aforementioned decrease in the amount of runway needed for an RTO, and, secondly, to the ability to reduce or eliminate the large number of crashes caused, for instance, by pilots rejecting at high speeds for blown tyres) - so why can’t or don’t aircraft manufacturers build autoRTO capability into their product offerings?

What if one of those automated systems fails during an auto-takeoff and the pilot hasn't hand-flown a take off in a year, or a month, or even a week? Piloting is a perishable skill (much like driving) and takes regular practice to keep the skills fresh. That's why pilots don't fly auto-land every time - the systems aren't available everywhere, they can fail, and when they do, the pilot needs to be 100% on his game.

What about a deer on the runway?
What about a BANG coming from the back somewhere?
What about a bird strike?
What about some indistinct object down the way that looks like it could be an airplane encroaching on the runway?
What about a WARNING light coming on?
What about a weird vibration starting?
What about an engine starting to stall/surge (whoomp whoomp whoomp) some time in the roll?
Rejects, especially high energy ones above the high energy threshold speed (it's why there is a speed call usually 80 or 90 kt) are considered high risk activities and often involve snap judgement calls. You will reject with less of a prompting if you are still in the low energy phase.
There are times when a pilot will reject even though he's just passing V1, if something happens that leaves doubt as to flyability and the runway is longer than necessary so there is still margin to stop.  You have a second to decide.
It's not something you can automate.  Way too many variables.

@ymb1: And for which pilots are prone to rejecting even well above V1.

@ymb1 that was one of the implied possibilities of BANG.

Yep.  A tire blowing is another judgement call that varies with circumstances.  If the runway is barely long enough, and I'm just shy of V1, where a blown tire means a probable overrun, I might continue and takeoff and head over to an airport with a long runway to land on.  If the runway has ample stop margin, I'd probably reject and take my chances with what I had.

And why should the pilot trust an automated rejection system if there's already failures with the aircraft? Something's definitely not right with his machine, why trust any part of it, eh?

"just passing V1 [...] the runway is longer than necessary so there is still margin to stop" Isn't the airplane by definition then below V1?

Theoretically, the plane's systems would know about the WARNING light even before the bulb illuminated and would be able to react more quickly. However, if it's a warning, is it one worth an RTO, or is it one that we can continue with...

@aCVn: No, V1 does not depend on runway length. See https://aviation.stackexchange.com/q/3564/17780

@Freeman the general protocol is most warnings and cautions are inhibited by warning system logic during the takeoff phase until you're climbing out, but some aren't. But you won't cancel a takeoff post V1 just because of a light.  It has to be something that is so severe you think it might be a really bad idea to get airborne, like a loud bang and crazy vibrations that makes you think "screw this I'll take my chances with an overrun".  If your minimum accelerate-stop distance was say 6000 ft and you are on a 10000 ft runway, that decision can be a bit easier.

"What about a warning light coming on?" is a bad example. Clearly the computer system that turned on the light could also initiate other action. Also, while you've convincingly argued that we can't automate all cases, you don't address the possibility of automating some cases. (Nonetheless, +1)

I don't disagree with your answer, but I feel that "way too many variables" isn't a reason for not automating - if anything, reducing complexity (by relieving the operator from having to deal with the unimportant variables) is usually a good reason for automating. The problem is that any or all of the variables could turn out to be important, so you wouldn't want to take that control and awareness away from the pilot or make them wrestle for it at critical moments. At least not until AI can surpass humans where it matters.

@bogl: Your link does not support your comment.

I believe it does, but possibly it is not explicit enough to convince people who think otherwise. What is your point @Sean? Do you challenge the statement, or is it merely about the link?

@bogl: The linked answer explains that V1 has to be low enough that the aircraft can stop on the remaining runway if an RTO is initiated before or at V1, while still long enough that the aircraft can continue the takeoff, lift off, and clear all obstacles by at least 35 feet if an engine fails too late for an RTO to be initiated before or at V1.  The upper limit depends (among other things) on how much runway is left for an RTO after reaching a particular speed, while the lower limit depends (among other things) on how much runway is left to accelerate to liftoff after reaching said speed.

The way it works in practice is that there is a single V1 speed per weight graduation, say every 2000lbs, with a correction factor for temperature, anti-ice on, etc.  The numbers are in the QRH and are usually reproduced as a booklet called a "speed book" or "speed cards".  You pick the speed card for your weight and input the numbers.  Before you get to that, however, you consult a "runway analysis chart" for a given runway, and the analysis chart tells you at what maximum weight you can depart for the temperature, etc. It saves you from laboriously working it out from AFM performance charts.

@Sean, the linked answer explains what V1 is made of, and runway length is not part of it. The minimum runway length depends on the actual V1, not the other way round. Runway analysis is done after determining V1.

Stopping after V1: I think the hydraulics are bad but the thrust reversers are OK.


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At what rpm does the tip of a 54" propeller start to incur mach losses?
At what rpm does the tip of a 54 inches propeller start to incur mach losses? The max rpm of my engine is 3600.

I think mach loss requires a forward speed as well as a tip velocity to calculate. At rest, your 54" diameter prop would need to be rotating at ~4800 rpm for the tips to approach mach 1...

A 54 inch propeller would start to incur efficiency loss at approximately 4300 rpm.
At 4300 rpm a 54 inch propeller would have a tip speed of 691 mph which, relative to the 767 mph speed of sound, is about the maximum which still allows propeller efficiency.
You can calculate the variables using this tool: WarpDriveProps.com Propeller Tip Speed Calculator

Flight speed and disk loading should also be considered. Your number looks right for a lightly loaded prop in a ground test.

Can you explain why 691 is "just below" 767? Is that the 0.92 comment from the embedded screenshot?

Yes, “just below” was taken from the screenshot and was poor wording on my part. I edited the answer. Thanks.

Assuming you have properly sized the prop for mission and power, peak performance is 0.8-0.9 mach as shown in comments and other answers. Aim low if your prop has fat or blunt tips. You would normally also consider advance ratio (helix) but in a slower aircraft this won't have much effect.
If you consider all losses (not just mach) you might ask what prop speed gives peak efficiency, and it is slower. I usually consider 0.65-0.75 mach a better target because efficiency gives me range. It is also quieter. Every prop is different but here are a couple of examples. They are RC props because data was available, and the curves give indications. I wouldn't believe any exact numbers.

Seeing as the efficiency in that graph seems to go to zero around Mach 0.8 - 0.9, how are supersonic propellers (such as that in the Thunderscreech) able to produce any thrust at all?

These are two particular props and not representative of every possible configuration. I'd be very interested in a Thunderscreech efficiency chart if you have one. 450kt in a prop plane is impressive, even if it used 6k shp to get a single seater there.

.....at the first sign of motion?  Seriously, the instant a propeller blade - like any object moving through a fluid - starts moving, it’s creating drag as it takes energy to displace the fluid in its path of motion.  That applies to the entire surface of the prop, not just the tip.

The question has been edited to be (IMO) a completely different one; this is a great answer for the original.

Yes it was,had to edit the question cos' I didn't ask as intended at first.


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Is it a good thing that ailerons remain deflected and the stick is hard to move?
The aileron stick of my homebuilt ultralight is stiff (hard to move) and the aileron itself can remain in its deflection angle hands free, is that a good thing?

Please take care to give your questions descriptive titles. "Homebuilt Airplane" does nothing to summarize the question you are asking here. I note that several of your previous questions have had similarly poor titles as well.

Your ultralight isn't flying yet, correct? Is the aileron getting stuck even when the wind is forcing it back to neutral, or simply on the ground in still air?

On the ground@Ben

It should not be stiff and hard to move, but remaining deflected on the ground is OK.

Hard to move is bad generally, it generally shouldn't take much effort to move your control surfaces.

OK thanks a lot sir.

The controls of any aircraft should move easily under the pilot's control.  Large aircraft have hydraulic servos to assist the pilot, or even complete fly-by-wire systems, while smaller aircraft often have aerodynamic trim tabs which act as a simple assistance mechanism.  On the ground, with no aerodynamic loads, the controls should move easily without such assistance, especially on an ultralight.
I would suspect that your control cables or pulleys are binding on something, or that the pivots of your cockpit controls or control surfaces are over-tightened.  Either of these could result in premature wear and failure in flight, as well as the more obvious difficulty in maintaining control before failure.  You should definitely investigate the cause thoroughly before attempting flight.